1. Field of the Invention
The present invention relates to display control unit and display control method, and more particularly to display control unit and display control method for quantizing input data to binary data or multi-value data and sending it to a display apparatus.
2. Related Background Art
A display apparatus is essential to an information processing apparatus for text and image, such as, word processor, personal computer or workstation.
Recently, as the information is distributed in multi-media and a processing performance of the information processing apparatus is improved, the display apparatus is required to display more information.
As a result, a display apparatus capable of not only monochromatic display but also gray level or full color animation display is required.
On the other hand, from the standpoint of cost reduction of the apparatus due to down-sizing and technology advancement and improvement of the office environment, the desk personalization of the information processing apparatus, that is, a trend of one unit per person is being enhanced, and from the standpoint of effective utilization of office space, reduction of the size and thickness of the apparatus is desired.
In the past, such a display apparatus would include a Braun tube display apparatus (CRT) and a liquid crystal display apparatus (LCD).
Of those, the former one, that is, the CRT, has a high display performance but is very expensive, and the latter one, that is, the LCD, includes several types which are generally thin but have some problems, respectively.
To achieve high display performance, a TFT liquid crystal display apparatus which has a drive element for each pixel is known. Since the drive elements are mounted on a surface of a liquid crystal glass, it has a low aperture factor and the display screen is dark. Further, the yield is low and a large size and fine screen is difficult to attain, and the cost is expensive. Accordingly, the TFT liquid crystal display apparatus is not yet common as a display apparatus for an information processing apparatus.
A simple matrix type STN liquid crystal apparatus which is primarily used presently is a binary display type and includes problems in display performance such as low contrast, cross-talk and a narrow viewing angle.
For a simple matrix type apparatus, a ferroelectric liquid crystal display apparatus (FLCD) which uses ferroelectric liquid crystal cells having a memory property is known. It does not have problems of contrast, viewing angle and cross-talk, but it can only make binary display at the present time.
When an image signal to be displayed is binarized, it will be very effective from the standpoint of improving the display performance if some image processing is performed to produce a quasi-gray level expression of an overall image to be displayed.
An error diffusion method which is a density reservation type binarizing method is known as a method for binary expression of the gray level. However, this method has the associated problems of reduction of resolution power, moire and lumbrical noise in the process of binarization. Further, since the prior art method is applied to a still image, no attention is paid to a continuously changing image such as animation, that is, an image which varies time sequentially and hence the moire and noise appear prominently.